A loose knitted cuff can be remedied in two different ways. The method you choose depends on the fibre the cuff is made from and the amount of stitch detail you wish to retain. If the cuff is made from wool, then felting it slightly will tighten it up. If the cuff is made from cotton or another non-animal fibre, it can be adjusted to fit with clear elastic thread. Choose the method that works best for your individual project.
Determine that the cuff is made from wool, alpaca or mohair; any of these fibres felt well enough for this method. If you knit the cuff yourself, check the yarn label for details. If you are adjusting the cuff on a commercially made item, check the garment label or tag.
Fill the sink with hot water. Immerse the problem cuff in the water until it is saturated.
Pour a drop of baby shampoo the size of a dime onto the cuff.
Rub the cuff vigorously with your hands. The more friction you use, the more the cuff will shrink. Rinse the cuff with water and check the fit. If the cuff fits well, press out the water and allow it to air dry. If it is still too big, felt it a second time.
Thread the needle with 18 inches of clear elastic thread.
Tie a knot in the end of the thread. Make a row of 1/4-inch-wide stitches around the cuff. Position the row of stitches about 1/4 inch from the cuff edge.
Pull the thread to adjust the cuff to the right size, then knot to secure.
Make a second row of stitches parallel to the first at the other end of the cuff and secure. For most cuffs, two rows of stitching is enough. For cuffs over two inches wide, make a third row of stitches with the elastic thread evenly centred between the first two.
These directions work for any type of cuff from sweaters to hats and mittens.
Felting is irreversible. If you want a way to reverse the process, then choose the sewing method.